Cam assembly having multiple cams with integral cam positioning means thereon

ABSTRACT

A cam assembly having a plurality of separate cam members mounted on a single drive shaft is provided with detent means that are operable to align the cam members in a predetermined angular displacement relative to one another, and maintain that displacement during operation of the assembly. The detent means on each cam member are substantially identical so that any given pair of cam members or a suitably mated replacement cam member may be operatively interlocked in the desired predetermined angularly displaced relationship without requiring further alignment procedures. In one embodiment of the invention, a unique cam-shift member is provided for readily changing the relative angular displacement between adjacent cam members without requiring these members to be removed from a drive mechanism on which they are mounted.

United States Patent Wilson 1151 3,656,370 .1451 Apr. 18, 1972 [54] CAMASSEMBLY HAVING MULTIPLE CAMS WITH INTEGRAL CAM POSITIONING MEANSTHEREON [72] Inventor: Austin F. Wilson, Rochester, NH. [73] Assignee:General Electric Company 22 Filed: July 2, 1970 [21] Appl. No.: 52,019

52 Us. or. ..74/568 R p [51] Int. Cl ..Fl6h 54/04 [58} Field of Search..74/568 R, 568 M, 568 T, 571 'M;

200/38 R, 38 BA, 38 C, 38.CA

[56] References Cited UNITED STATES PATENTS 2,468,974 5/1949 Hammer.74/568 x 2,473,417 6/1949 Essl ..74/568 3,221,117 11/1965 Simmons74/568 X 3,499,347 3/1970 Pearson ..74/568 R27,04l 1/1971 Hotchkin..74/568 X FOREIGN PATENTS OR APPLICATIONS 592,147 9/1947 I England..74/568:

Primary Examiner-Milton Kaufman Assistant Examiner-F. D. ShoemakerAttorney-Francis X. Doyle, Vale P. Myles, Frank L. Neuhauser, Oscar B.Waddell and Joseph B. Forman [57] ABSTRACT A cam assembly having aplurality of separate cam members mounted on a single drive shaft isprovided with detent means that are operable to align .the' cam membersin a predetermined angular displacement relative to one another, andmaintain that displacement during operation of the assembly.

The detent means on each cam member are substantially 8 Claims, 8Drawing Figures PATENTEDAPR 18 1912 3, 656,370 SHEET 2 0. 2

0%]??? M19071, b y a .W

It is common practice in the prior art to use a plurality of cam membersmounted on a single drive shaft or other suitable mounting means tooperate as a control mechanism for selectively actuating a plurality ofswitches or other operating members in a predetermined sequence. In suchdevices, movably mounted cam follower members are positioned adjacentthe respective cam members on the drive shaft in a manner such thatrotation of the shaft causes the cam surfaces of the cam members to movethe cam followers in a given preset pattern. In order to determine adesired sequence of operation of the cam follower-actuated operatingmembers it is necessary to carefully orient the respective cam memberswith respect to one another and then lock them in this relativeposition. Prior to the present invention, such cam member orienting andlocking functions were normally performed manually by individuallyadjusting each cam member to a given alignment with respect to the shaftand then locking the member to the shaft.

In addition to having the disadvantage of being very expensive to placein a desired operating relationship, such prior art multiple-cam memberassemblies also tended to become unaligned during operation when one ormore of the cam member locking means allowed its cam member to slip withrespect to the operating shaft and the other cam members. Moreover, inthese prior art assemblies no simplified cam alignment and locking meanswas provided for quickly adjusting the predetermined axial displacementbetween given pairs of cam members in order to effect a desiredvariation in the operating sequence of the operated members moved by thecam followers.

A primary object of the present invention is to provide an improvedmultiple-cam member assembly having cam orienting and positioning meansthat are more efficient to manufacture and operate than cam positioningmeans heretofore known.

Another object of the invention is to provide a mechanically simple andyet rugged cam orienting and positioning means for a plurality ofinterrelated cam members of a multiple-cam assembly, which are readilyoperable to align and maintain the respective cam members in apredetermined operating positron.

Yet another object of the invention is to provide a cam assembly havinga plurality of cam members rotatably mounted on a drive shaft andprovided with inter-locking detent means that are operable to orient andposition the respective cam members in a predetermined desiredrelationship on the shaft by simply biasing the respective detentmembers into interlocking engagement with one another.

Still another object of the invention is to provide a simplifiedcam-shift member that is adapted to operate cooperatively with premoldeddetent means on a pair of cam members that are normally operable by asingle drive mechanism on which they are maintained at a predeterminedangular displacement with respect to one another. The cam-shift memberis operable to easily vary the relative angular displacement between thetwo cam members without requiring them to be removed from the drivemechanism.

In one preferred embodiment of the invention, a cam assembly is providedwith a plurality of rotatable cam members mounted on a single driveshaft. Each of the cam members is generally in the configuration of adisc having a cam-actuating surface on its circumference and havingmolded detent and projection means on each of its sides. Pursuant to theinvention, the detent and projection means for each cam member aresubstantially identical and they are adapted to be moved intointer-locking engagement with respect to one another when the cammembers are biased together, thereby to align and maintain the cammembers in a predetermined angular displacement with respect to oneanother on the drive shaft. This predetermined angular displacement ofthe respective cam members allows them to operate associated camfollowers that are riding on their respective cam surfaces through adesired sequence of operating patterns relative to one another. In oneembodiment of the invention, a cam-shift member is provided for quicklyand easily varying the relative angular displacement between the two cammembers. This cam shift member can be inserted between the two cammembers and snapped into operating position on the drive shaft withoutrequiring either of the cam members to be removed from the drive shaftor from operating contact with their associated cam followers.

Additional objects and advantages of the invention will become apparentfrom the description that follows taken in conjunction with the attacheddrawings in which:

HG. l is a perspective view of a portion of a cam assembly constructedpursuant to the present invention and shown with respect to a pair ofoperating members in the form of electrical contacts that are actuatedby movement of cam followers riding on cam members of the assembly.

FIG. 2 is a perspective view of a cam stop member or positioning meanssimilar to a cam member positioning means shown in the assembly of FIG.1 and interchangeable therewith.

FIG. 3a is a side elevation view of one of the cam members shown in theassembly of FIG. 1.

FIG. 3b is a top plan view of the cam member shown in FIG. 3a.

FIG. 3c is another side elevation view of the cam member shown in FIGS.3a and 3b showing the side thereof opposite to the side illustrated inFIG. 3a.

FIG. 4a is a side elevation view of a cam-shift member constructedpursuant to the invention and adapted to be used in cooperation with thecam members illustrated in the assembly of FIG. 1 of the drawing tochange the relative angular displacement between these members in apredetermined manner.

FIG. 4b is a top plan view of the cam-shift member illus trated in FIG.40.

FIG. 40 is a side elevation view of the cam-shift member shown in FIGS.40 and 4b and depicting the other side of this member.

Referring now to FIG. ll of the drawing, there is shown a cam assembly 1comprising a plurality of separable cam members 2 and 3, which aregenerally disc-shaped in configuration and include respective camsurfaces 4 and 5 on the circumferential edges thereof. The cam surfaces4 and 5 in this embodiment of the invention are in the form of aplurality of tooth-like projections, but other configurations mayobviously be used, as will be apparent from the following description,without impairing the operability of the present invention. A pair ofindependently movable cam followers 6 and 7 are mounted in contact withthe cam surfaces 4 and 5 respectively and are pivoted on a suitable rod8, which in turn is supported by a pair of mounting brackets 9 and 10.The cam followers 6 and 7 each comprise a rod-like arm member 6' and 7',respectively, on which there is mounted a pair of movable electricalcontacts 111 and 12. The contacts 11 and 112 are adapted to be closedrespectively onto relatively fixed contacts 13 and 14, which are mountedon the support members 9 and 10. It should be understood that camfollowers 6 and 7 are biased by gravity into contact with tooth-likesurfaces t and 5 respectively; however, other biasing means, such assuitably mounted springs (not shown) may be used if desired.Alternatively, the arms 6' and '7' may be made of leaf springs that areclamped in a preset position with respect to mounting brackets 8 and 9,rather than being pivoted thereon, if such an arrangement for biasingthe cam followers is desired. Also, it will be appreciated that suitableoperating circuitry will normally be connected to the contacts 11-13 and12-14; however, since such circuitry does not affect the inventiondisclosed herein, it is not illustrated in the embodiment of theinvention shown in FIG. ll. Finally, although cam members 2 and 3 andmounting brackets 8 and 9 are shown in FIG. l in a spaced-apart mode, aswill be apparent from the following description, these components willnormally be mounted closely adjacent one another when assembly 1 is inoperating position.

As can be seen in FIG. 1, a suitable mounting means in the form of adrive shaft is provided for supporting each of the cam members 2 and 3in an operably movable position with respect to the cam followers 6 and7. It should be understood that the cam members 6 and 7 each have anaperture through their center which is slightly larger than the diameterof the drive shaft 15 so that these cam members can slide easily withrespect to the longitudinal axis of this drive shaft. A suitable drivemeans 16, which may be in the form of an electric motor or any otherconventional drive mechanism, is coupled to the drive shaft 15 andoperable to rotate the drive shaft in a clockwise direction as seen inFIG. 1. On the other end of drive shaft 15, a stop member 17 in the formof a disc is locked in position with respect to the shaft by a lockscrew 18 mounted in a threaded aperture through a shank on the stopmember 17. In addition, the stop member 17 comprises an elongatedprojection 19 on one side thereof which is adapted to engage the cammember 3 in a manner that will be described in more detail below,thereby to provide a driving coupling for the cam member 3.

Pursuant to the present invention, both of the cam members 2 and 3 areprovided with a plurality of substantially identical, cooperativelyinter-locking detent means that are mounted on the side surfacesthereof. On the cam member 2, these detent means comprise a pair ofelongated, generally parallel projections-20 and 21 on one side of thecam member 2 and a single elongated projection 22 on the other sidethereof. In like manner, the cam member 3 is provided with a pair ofelongated generally parallel projections 23 and 24 on one side thereofand a single elongated projection 25 on its other side. Each of thesingle elongated projections 22 and 25 are adapted to slide intointer-locking engagement with a cooperating pair of parallel projectionson an adjacent cam member, for example, the projection 25 is adapted toslide into inter-locking engagement with the pair of parallelprojections 20 and 21 on the cam member 2. In fact, in accordance withthe invention, when the cam members 2 and 3 are assembled in operatingposition they will be biased into abutting relationship so theprojection 25 on cam member 3 is locked in position between the pair ofparallel projections 20 and 21 on cam member 2 thereby establishing apredetermined orientation and relative angular displacement betweenthese two cam members. Further, in such an operating position, the cammember 3 is biased against the stop member 17 in a manner such that theprojection 19 on this stop member is positioned in inter-lockingengagement with the pair of parallel projections 23 and 24 on the cammember 3, and a slidably mounted locking means in the form of areleasable lock mechanism 26 on an annular ring having a set screw 27mounted therein in conventional manner is moved into abutting contactwith the inner surface of projection 22 on cam member 2 thereby tomaintain the detent means in their respective inter-locked positions.

It can thus be seen that when the cam assembly 1 is arranged in itsoperating position with the respective cam members 2 and 3 biased towardthe stop member 17, and interlocked therewith by the locking means 26, apredetermined angular displacement has been quickly and positivelyestablished between these respective cam members so that the camfollowers 6 and 7 are actuated thereby in a predetermined sequence. Ofcourse, it will also be apparent that the rate of operation of either ofthe pairs of contacts 11-13 or 12-14 can be varied by changing thenumber of tooth-like projections on either or both of the cam members 2and 3. In addition, due to the novel arrangement of the presentinvention, it is possible to quickly and easily change the relativeoperating sequence of the two pairs of contacts 11-13 and 12-14. In thisregard, it must be understood that in practicing the present inventionthe cam members 2 and 3 are preferably formed of thermal plasticmaterial that is easily molded into precisely controllableconfigurations so that the generally disc-shaped cam members and theirassociated detents and projections are all integrally formed. Also, withany given cam assembly in which it may be desired to change the relativeangular displacement between associated contact members, such as themembers 2 and 3 of the assembly 1, a number of difierent cam memberswill be manufactured with various numbers of cam actuating tooth-likeprojections on the surface thereof, but each having substantiallyidentical detent and projection means mounted on the respective sidesthereof, so that these other cam members can be substituted for eitheror both of the cam members 2 and 3 by simply loosening set screw 18 instop member 17 and sliding the stop member 17 and the cam members to beremoved off of the shaft 15 so that the new cam members can besubstituted in their place and the assembly reassembled. Moreover, aswill be described in greater detail below, the present inventionprovides a unique means for varying the relative angular displacementbetween two cam members, such as the members 2 and 3 without requiringeither of them to be removed from operating position.

Various modifications of the embodiment of the invention shown in FIG. 1will be apparent to those skilled in the art. However, it is noted herethat frequently in cam assemblies it is desirable to provide a pluralityof cam-follower actuating members that are locked in a predeterminedrelative angular displacement with respect to one another, but which areotherwise free to rotate in an idling manner, i.e. without beingdirectly subjected to a driving motion from a shaft, such as shaft 15.An embodiment of the invention, partially depicted in FIG. 2 of thedrawing, is designed to afford such a mode of operating the invention asit is depicted in FIG. 1. As shown in FIG. 2, in which the samereference numerals are used to indicate parts identical to those used inFIG. 1, there is shown a portion of shaft 15 on which is mounted thestop member 17. In this fonn of the invention, the stop member 17 is notprovided with a projection, such as the projection 19 illustrated inFIG. 1, therefore, when a cam member such as cam member 3 is biasedagainst the stop member 17, it will simply be prevented from furtheraxial movement along the shaft 15, but it will not be restricted fromangular or rotary movement with respect to the shaft.

In order to more clearly describe the unique inter-locking detent meansof the invention, a detailed illustration of one of the substantiallyidentical cam members, in this case cam member 2, illustrated in FIG. 1,is shown in FIGS. 3a, 3b and 3c. Again, the same reference numerals areused in FIGS. 311-30 to designate component parts similar to thosediscussed above with reference to FIG. 1. Thus, on one side of thegenerally disc-shaped cam member 2 there is shown in FIG. 3a a pair ofelongated generally parallel projections 20 and 21 that define achannel-like detent 30 therebetween. On the other side of the cam member2, as seen in FIG. 3c, a single elongated projection 22 is provided.According to the present invention, the width of the projection 22 isslightly smaller than the width of the channel-like detent 30 on theopposite side of the member 2, so that other cam members havingidentically formed detents and projections can be biased intointer-locking engagement with one another in the manner described above.As can perhaps be best seen in FIG. 3c, the longitudinal axis of thesingle projection 22 is angularly displaced by a predetermined angle,indicated by the arrow 31, with respect to the longitudinal axis of thechannel-like detent 30. Thus, assuming a cam member 3 havingsubstantially identically formed detent and projection means on therespective sides thereof is moved into inter-locking engagement with thedetent or projection means on cam member 2, the two cam members wouldthereby be quickly and easily oriented so that their respective singleprojections 22 and 25 would be displaced from one another by thepredetermined angle indicated by the arrow 31. Of course, this angle isfixed permanently for any given set of molded cam members having detentmeans of the invention formed thereon. However, a

description will now be given of a further improvement of the presentinvention that provides a means for varying the relative angulardisplacement between cooperating cam members, such as the members 2 and3.

In order to describe this modification of the present invention,reference is now made to FIGS. ta-4c of the drawing, in which there isshown a generally disc-shaped, thermal plastic, molded cam-shiftingmember constructed pursuant to the teaching of the invention. Thecam-shift member 32 has a pair of generally parallel projections 33 and34 integrally formed on one side thereof and a single elongatedprojection 35 on the other side thereof. The angular projections 33 and34 define a channel-like detent 36 therebetween, which is sub- 1stantially equal in width to the channel-like detent 30 in cam member 2.Also, the single projection 35 is substantially identical in width tothe projection 22 on cam member 2. Thus, it will be understood that thecam-shift member is adapted to be operatively mounted between a pair ofcam members such as the cam members 2 and 3 illustrated in the assembly1 and interlocked in engagement with the detents and projections onthese abutting cam members. The important unique feature of thecam-shift member 32 is that the relative angular displacement betweenthe longitudinal axis of projection 35 and the parallel projections 33and 34 thereon, as shown by the arrow 37 in FIG. 4c is different (thatis, either larger or smaller, as desired) than the angular displacementindicated by the arrow 31 in FIG. 3c. Thus, it will be apparent thatwhen the cam-shift member is inter-locked in position between a pair ofcam members such as the members 2 and 3, the relative angulardisplacement between these cam members is changed with respect to'theangular relationship maintained between them when they are directlyinter-locked together by their associated detents and projectionsthereon. Accordingly, by simply placing the cam-shift member 32 in suchan operating position, it is possible to quickly and easily change theangular displacement of two or more of the cam members on drive shaft15. It should be understood that a plurality of cam-shift members eachhaving different or the same relative angular displacements betweentheir channel-lil e detent and oppositely disposed parallel projectionscan be provided for any given cam assembly such as the assembly 1 sothat a number of different relative angular displacements may be easilyprovided at different times between the respective cam members 2 and 3thereof. It should also be recognized that two or more of the cam-shiftmembers, such as the shift member 32, may be used simultaneously toprovide different combinations of relative angular displacement betweenthe respective cam members 2 and 3.

A further important feature of the cam-shift member 32 is the provisionof means defining a slot 38 from the periphery thereof to the annularaperture 39 at the center thereof. In the preferred embodiment of theinvention, the thermal plastic material of which cam-shift member 32 isformed is sufficiently resilient to allow the side walls of the slot 38to be resiliently biased slightly outward as it is forced over the shaftso that it can be quickly and easily snapped into position on the shaft15 without requiring either of the cam members 2 or 3 to be removed fromoperating position. Thus, the walls of slot 38 comprise a resilientlocking means that is operable to be biased into position to hold thecam-shift member 32 in operating position. Therefore, it is possible tochange the relative angular displacement of the cam members 2 and 3 ofthe assembly 1 of the invention without requiring any portion of theassembly 1 to be dismantled to effect such a change.

Further advantages and modifications of the invention will becomeapparent to those skilled in the art and all such embodiments of theinvention are intended to be encompassed within the scope of thefollowing claims.

Iclaim:

l. A cam assembly comprising a plurality of separable cam members eachof which include a cam surface for moving a cam follower, at least twoindependently movable cam followers, each of said cam followers beingmounted adjacent to and in contact with one of said cam surfacesrespectively to be moved thereby in response to movement of saidsurfaces, mounting means for supporting each of said cam members in anoperably movable position with respect to said cam followers, aplurality of cooperatively inter-locking detent means respectivelymounted on abutting surfaces of said cam members and operable wheninterlocked with one another to prevent relative movement between saidcam members and to maintain the respective surfaces of said cam membersin a predetermined relative angular position with respect to oneanother, said predetermined position being effective to establish asingle given preselected angular displacement between the respective camsurfaces on said cam members, and locking means for maintaining saiddetent'means in their respective interlocked positions, said lockingmeans being releasable thereby to facilitate relative movement of saidcam members to at least one other predetermined relative position inwhich the detent means are effective when again interlocked to preventrelative movement of said cam members.

2. A cam assembly as defined in claim 1 wherein each of said cam membersand the respective detent means thereon are formed from an integrallymolded thermal plastic material, said cam members being generallydisc-shaped with cam surfaces fonned on the circumference thereof, andsaid detent means comprising spaced-apart detents and projections in theside surfaces of said discs.

3. A cam assembly comprising a plurality of separable cam members eachof which include a cam surface for moving a cam follower, at least twoindependently movable cam followers each of said cam followers beingmounted adjacent and in contact with one of said cam surfacesrespectively to be moved thereby in response to movement of saidsurfaces, mounting means for supporting each of said cam members in anoperably movable position with respect to said cam followers, aplurality of cooperatively inter-locking detent means respectivelymounted on abutting surfaces of said cam members and operable wheninterlocked with one another to prevent relative movement between saidcam members and thereby maintain said cam members in a predeterminedrelative position with respect to one another, and locking means formaintaining said detent means in their respective interlocked positions,said locking means being releasable thereby to facilitate relativemovement of said cam members to at least one other predeterminedrelative position in which the detent means are effective when againinterlocked to prevent relative movement of said cam members, theconfiguration of the detents and projections on each of said cam membersbeing substantially identical thereby to enable given cam members to beinterchanged with respect to one another and still afford acooperatively interlocking relationship therebetween, each of said cammembers having a pair of elongated generally parallel projections on oneside thereof with a detent channel therebetween and having a singleelongated projection on the other side thereof, each of said singleelongated projections being adapted to slide into inter-lockingengagement with a pair of parallel projections on an adjacent cammember.

4. A cam assembly as defined in claim 3 wherein the iongitudinal axis ofthe single elongated projection on one side of a cam member is angularlydisplaced with respect to the axis of said cam member in relation to thelongitudinal axes of the pair of elongated generally parallelprojections on the other side thereof.

5. A cam assembly as defined in claim 2 including a camshift memberoperatively mounted between a pair of said cam members, said cam-shiftmember having projections on opposite sides thereof that are adapted tofit in inter-locking engagement with the detents and projections on thecam members abutting it, the projections on opposite sides of saidcamshift member being mounted in a predetermined relatively angulardisplaced position with respect to one another, thereby to cause arelative angular displacement between a pair of cam members with whichit is inter-locked with respect to the angular relationship maintainedbetween said pair of cam memsaid mounting means.

8. A cam assembly as defined in claim 7 wherein said resilient lockingmeans comprises a generally disc-shaped resilient member having meansdefining a radial slot therein from the periphery to the center thereof,said slot being adapted to be resiliently slipped onto the mountingmeans for said cam members thereby to hold the cam-shift member inoperating position.

1. A cam assembly comprising a plurality of separable cam members eachof which include a cam surface for moving a cam follower, at least twoindependently movable cam followers, each of said cam followers beingmounted adjacent to and in contact with one of said cam surfacesrespectively to be moved thereby in response to movement of saidsurfaces, mounting means for supporting each of said cam members in anoperably movable position with respect to said cam followers, aplurality of cooperatively inter-locking detent means respectivelymounted on abutting surfaces of said cam members and operable wheninterlocked with one another to prevent relative movement between saidcam members and to maintain the respective surfaces of said cam membersin a predetermined relative angular position with respect to oneanother, said predetermined position being effective to establish asingle given preselected angular displacement between the respective camsurfaces on said cam members, and locking means for maintaining saiddetent means in their respective interlocked positions, said lockingmeans being releasable thereby to facilitate relative movement of saidcam members to at least one other predetermined relative position inwhich the detent means are effective when again interlocked to preventrelative movement of said cam members.
 2. A cam assembly as defined inclaim 1 wherein each of said cam members and the respective detent meansthereon are formed from an integrally molded thermal plastic material,said cam members being generally disc-shaped with cam surfaces formed onthe circumference thereof, and said detent means comprising spaced-apartdetents and projections in the side surfaces of said discs.
 3. A camassembly comprising a plurality of separable cam members eAch of whichinclude a cam surface for moving a cam follower, at least twoindependently movable cam followers each of said cam followers beingmounted adjacent and in contact with one of said cam surfacesrespectively to be moved thereby in response to movement of saidsurfaces, mounting means for supporting each of said cam members in anoperably movable position with respect to said cam followers, aplurality of cooperatively inter-locking detent means respectivelymounted on abutting surfaces of said cam members and operable wheninterlocked with one another to prevent relative movement between saidcam members and thereby maintain said cam members in a predeterminedrelative position with respect to one another, and locking means formaintaining said detent means in their respective interlocked positions,said locking means being releasable thereby to facilitate relativemovement of said cam members to at least one other predeterminedrelative position in which the detent means are effective when againinterlocked to prevent relative movement of said cam members, theconfiguration of the detents and projections on each of said cam membersbeing substantially identical thereby to enable given cam members to beinterchanged with respect to one another and still afford acooperatively inter-locking relationship therebetween, each of said cammembers having a pair of elongated generally parallel projections on oneside thereof with a detent channel therebetween and having a singleelongated projection on the other side thereof, each of said singleelongated projections being adapted to slide into inter-lockingengagement with a pair of parallel projections on an adjacent cammember.
 4. A cam assembly as defined in claim 3 wherein the longitudinalaxis of the single elongated projection on one side of a cam member isangularly displaced with respect to the axis of said cam member inrelation to the longitudinal axes of the pair of elongated generallyparallel projections on the other side thereof.
 5. A cam assembly asdefined in claim 2 including a cam-shift member operatively mountedbetween a pair of said cam members, said cam-shift member havingprojections on opposite sides thereof that are adapted to fit ininter-locking engagement with the detents and projections on the cammembers abutting it, the projections on opposite sides of said cam-shiftmember being mounted in a predetermined relatively angular displacedposition with respect to one another, thereby to cause a relativeangular displacement between a pair of cam members with which it isinter-locked with respect to the angular relationship maintained betweensaid pair of cam members when they are directly interlocked together bythe detents and projections thereon.
 6. A cam assembly as defined inclaim 5 wherein said cam-shift member includes a resilient snap-actionlocking means for releasably holding it in operating position betweensaid pair of cam members.
 7. A cam assembly as defined in claim 6wherein said resilient locking means is operable to enable saidcam-shift member to be placed in operating position between said pair ofcam members without requiring the removal of them from said mountingmeans.
 8. A cam assembly as defined in claim 7 wherein said resilientlocking means comprises a generally disc-shaped resilient member havingmeans defining a radial slot therein from the periphery to the centerthereof, said slot being adapted to be resiliently slipped onto themounting means for said cam members thereby to hold the cam-shift memberin operating position.